Lipids Fatty acids FAs o Straight HC chains o Saturation Can be 4 24 carbons long 14 or more C are nutritionally significant Most FAs are even Cs Saturated FA Solid at room temp s for solid All C s are saturated with H s No Double Bonds DBs Animal fats Monounsaturated FA 1 DB Olive oil canola oil Polyunsaturated FA Multiple DB DB s are always 3 carbons apart Cis form is predominant Trans fats are produced via food processing o Short chain 3 C o Medium chain 4 12 C 10 is the usual amount o Long chain 14 C o Unsaturated fats are liquid at room temp Hydrogenation o Adding H s to unsaturated fat to make it solid at room temp Crisco margarine o Makes plant oils solid at room temperature o Often used in commercially processed foods o Convert cis bonds to trans Hydrogenation forms fats trans How to name a fatty acid o Count number of C s o Count the number of double bonds o Name according to the omega Methyl n omega the tail end or alpha alpha carboxylic delta the head end From omega end tail count in from omega end and label the 1st double bond with the C number From alpha end head count in from alpha end and label ALL double bonds o All double bonds in a fatty acid are 3 carbons away from each other o Linoleic acid 18 2 omega 6 or 18 2 delta 9 12 o Alpha Linolenic acid 18 3 omega 3 or delta 9 12 15 o We lack the enzymes to add double bonds beyond the delta 9 position This makes these FAs essential because it is essential that we eat Essential fatty acids Trick Recall from proteins essential AAs Can you name them them all Eicosanoids o NSAID NonSteroidal Anti Inflammatory Drugs inhibit eicosanoid formation o Families o Hormone like substances o Modulation of Blood pressure Platelet aggregation Immune system Nervous system Smooth muscle contraction Prostacyclins Thromboxanes Leukotrienes o Synthesized from Arachidonate acid 20 4 omega6 Eicosatrienoic acid 20 3 omega 6 Eicosapentanoic acid 20 5 omega 3 o Omega ratio o Male Linoleic Acid Omega 6 16 17 g day Alpha Linolenic Acid Omega 3 1 6 g day o Female Linoleic Acid Omega 6 11 12 g day Alpha Linolenic Acid Omega 3 1 1 g day Deficiencies in specific eicosanoids determine which eicosanoids are produced vasodilator vasoconstrictor etc Triglycerides o Glycerol backbone 3C chain and 3 FAs o FAs can vary in length and saturation o We eat and then store in adipose tissue o We can use them individually Phospholipids o Phosphate head o Glycerol backbone o 1 FA Glycolipids o Lipid and CHO carbohydrate head Single CHO String of CHOs Branched CHOs Sterols o Steroid nucleus o Cholesterol is precursor for Sex hormones Bile acids Adrenocorticoids Vitamin D o Found in animal products o ONLY animals need cholesterol we make and eat it TOPHAT where do we use the majority of phospholipids in our body Cell membrane in the phospholipid bilayer Lipid digestion o Lingual lipase Secreted at the base of the tongue Stable at a low pH Used in the digestion of milk fat Infants o Biliary emulsification Emulsification Dispersion of fat in an aqueous solution Allows for lipase action Bile salts emulsifying agent Keeps the lipids hydrophobic and the Proteins and CHOs hydrophilic together in the lumen o Lipolysis Pulling off a FA from a glycerol backbone 3 main enzymes 1 Pancreatic lipase o Secreted from pancreas to small intestine o Breaks triglyceride into 3 FAs and a glycerol 2 Cholesterol esterase o Free cholesterol and a FA 3 Lecithinase o Lysolecithin and a FA Lipid absorption o Micelle formation o Inside the enterocyte Fatty elements and fat soluble vitamins surrounded by bile salts Passive diffusion of fatty elements and vitamins distal duodenum and jejunum Ex Fat Soluble Vitamins ADEK Bile salts are absorbed in the ileum and returned to liver via EHC Long chain FA s 12 C and other fatty components are activated with Coenzyme A Reformation of TGs cholesterol esters and phospholipids TGs Fatty Components Proteins Chylomicrons Short chain FAs are attached to albumin and transported to extra hepatic tissues TOPHAT When we elongate a FA using an elongase we change it from an omega 3 to an omega 6 False we never change the omega end Elongase connects C chains at the alpha end Lipoproteins Complexes which carry lipid products in the blood and lymph to various tissues A note on Lipoprotein lipase your perspective should be set within the chylomicron or the VLDL Wikipedia offers a clear explanation on this enzyme LPL is found inside of lipoprotein To understand this o http en wikipedia org wiki Lipoprotein lipase Chylomicron o Formation Synthesis in enterocytes from EXOGENOUS lipids Released into lymph o Composition Apoproteins ABCE TG s o Size 80 Phospholipids and cholesterol Largest lipoprotein and lowest density 90 100nm o Function Decreased protein percentage decreased density Transports exogenous triglycerides to tissues Lipoprotein lipase Hydrolyzes TG to free FA and glycerol Free FAs and glycerol absorbed into tissues o Chylomicron remnant Remains after TG hydrolysis Taken up by the hepatocytes via receptor mediated endocytosis Very Low Density Lipoprotein o Formation Synthesized in liver Released into blood o Composition 50 Apoproteins B and C TG s o Size Cholesterol and Phospholipids 30 90nm o Function Transports endogenous lipids from liver to extra hepatic tissues Tissues other than the liver Lipoprotein Lipase Hydrolyzes TG to free FAs and glycerol Free FAs and glycerol absorbed to tissues Intermediate Density Lipoprotein o Formation Made from VLDL after TG hydrolysis Transient very short lived o Function TOPHAT LPL only functions with IDL and VLDL False also works with chylomicron Formed into LDL after TG hydrolysis via LPL Low Density Lipoprotein o Formation o Functions From IDL after TG Hydrolysis Delivers cholesterol to extra hepatic tissues Uptake via receptor mediated endocytosis o Composition Apoproteins B 100 TG 9 Cholesterol The Big Kahuna 50 composition o Size Phospholipids 20 25nm Receptor medicated endocytosis o Receptors located in clathrin coated pits o Receptors are specific for proteins LDL have Apo B 100 o LDL and Receptor bind o LDL and Receptor complex internalize Forms vesicle o Vesicle fuses with lysosome o Apo B degraded to AA o Cholesterol is released into the cell o Receptor returns to the surface Regulation o HMG CoA reductase activity Rate limiting enzyme for cholesterol synthesis More cholesterol in cell HMG CoA reductase activity is reduced Decreased receptors synthesis no need to bring more cholesterol into the cell o LDL
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